Self-supporting filter element



Oct. 29, 1968 R. T. sTAuNToN 3,407,576

SELF- SUPPORTING FILTER ELEMENT Original Filed Feb. 5, 1964 INVENTOR.

United States Patent O 3,407,576 SELF-SUPPORTING FILTER ELEMENT RichardT. Staunton, Birmingham, Mich., assignor to G. S.

Staunton & Company, Inc., Birmingham, Mich., a corporation of MichiganContinuation of application Ser. No. 342,599, Feb. 5, 1964. Thisapplication June 14, 1966, Ser. No. 562,063 9 Claims. (Cl. 55-514) Thisinvention relates to filter elements and more particularly to aself-supporting filter element wherein the filter means is of a materialwhich is flexible and nonselfsupporting. This application is acontinuation application of the copending United States application,Ser. No. 342,599; filed on Feb. 5, 1964, now abandoned, in the name ofRichard T. Staunton.

In the design and manufacture of filter elements, such as of the typethat might be used for air conditioning units, furnaces or the like, theincreasing popularity of plastic foam materials for the filter elementpresents numerous problems. Theoretically, the filter element need onlybe thick enough to give the desired amount of filtration to the airpassing therethrough. However, such foam materials are usually of such afiexible nature that they do not support themselves in the apparatuswith which they are used when manufactured to the desired dimensions.When the filter elements become dirty and need to be cleaned orreplaced, it is highly desirable that they be of such construction thatthey are easily removed. Since the filter element is notself-supporting, elaborate fastening means are required to secure it inits filtering position in the apparatus, making it that much moredifficult for removal and/ or replacement. In order to overcome thisproblem, either the filter material must be made of such thickness anddensity to be self-supporting, which inordinately increases the overallexpense even though the overall air restriction efficiency of the unitis increased, or else some elaborate means must be taken to support thefilter material and provide a suitable frame structure. Such means,however, have in the past been extremely expensive and inefiicient, bothfrom the manufacture and the design standpoint.

It is here proposed to provide a filter element where the filtermaterial is of optimum density and thickness, even though it is flexibleand nonself-supporting. The procedure for forming the filter comprises,generally, the steps of placing a batt of such filter material in asuitable mold or die and overlying a series of cavities formed in acontinuous and predetermined pattern, such as about the periphery of thefilter batt. A thermosetting or thermoplastic material is injected intothe mold or die and into the continuous cavities, the materialincorporating the material of the filter batt overlying the cavities,and when the plastic material is cured, the resulting structure is ofsufficient strength and rigidity to support the exible filter batt andprovide a supporting frame `suitable for fitting into the apparatus withwhich the filter element is used.

It is apparent that a filter element constructed as proposed isextremely versatile in its design and manufacture possibilities. Thesize and shape of the lter element produced are limited only to the'size and complexity permissible in the die or mold, and convenientfastening means may be formed integrally with the frame structure toeliminate the necessity of elaborate and expensive separable fasteningdevices that might otherwise be required. The filter element makes useof materials which are suited to the use to which the element is to beput, such as, for example, a fiat filter element that may be slippedinto place in a furnace or air conditioning device, or a continuous beltof filter material that might be used 3,407,576 Patented Oct. 29, 1968'ice in a dehumidifier or the like, the frame structure being ofsufficient flexibility in the latter case 'to permit the filter elementto be formed into a continuous loop similar to a belt or chain. Theoverall result is a filter element of extreme versatility, relativelyinexpensive to manufacture and produce on a volume basis, and of optimumefficiency in its operation.

These and other advantages will become more apparent from the followingdescription in which:

FIGURE l is a plan view of a filter element manufactured in accordancewith the invention.

FIGURE 2 is a partial cross-sectional View of the filter elementillustrated in FIGURE 1, taken substantially along the line 2 2 ofFIGURE 1 and looking in the direction of the arrows, to illust-rate thestructure of the filter element.

FIGURE 3 is a -plan view of another filter element manufactured inaccordance with the invention.

FIGURE 4 is a cross-sectional view of the filter element illustrated inFIGURE 3, taken substantially along the line 4-4 of FIGURE 3 and lookingin the direction of the arrows.

FIGURE 5 is a diagrammatic illustration of the ap paratus by which thefilter elements of FIGURES l and 3 may be manufactured, utilizing themethod of the invention.

FIGURE 6 is a perspective view of yet another filter element embodyingthe method of the invention.

Referring more particularly to the drawing, FIGURE l illustrates onetype of filter element which may be of the type used in furnaces or thelike. The element includes a batt of filter material 10 which is ofsubstantially the overall size and shape of the completed element. Thefilter batt 10 may be formed of a plastic foam material which, in itsoptimum condition, is of flexible and nonself-supporting nature. Thatis, the filter batt by itself could not be used without elaboratefastening means to hold it in place and would not stand by itself in theapparatus with which it is used. To provide a stiffening means for thefilter batt 10, a framework, illustrated generally by the numeral 12, isprovided, and the assembly is manufactured in a manner to be hereinaftermore clearly described.

The supporting frame 12 is formed of a suitable thermoplastic orthermosetting plastic material which may be injection molded or extrudedto its proper form, and when so formed, will incorporate the adjacentportions of the filter batt 10 and provide a unitary or integral unit ofsufficient strength to be self-supporting.

In the embodiment illustrated in FIGURE l, the sup porting frame 12includes a peripheral portion 14 and a 'series of cross members 16forming a grid-like pattern over the filter batt 10. Since the filtermaterial is incorporated directly into the frame structure 12, as shownin FIGURES 2 and 4 and as will become hereinafter more apparent, eachindividual section, or group of sections, of the filter element will bea complete and separate element in itself. Thus, if a filter element ismanufactured, such as illustrated in FIGURE 1, with the nine separatesections shown and it is desirable to utilize only the lower right-handfour sections, the remaining five sections may easily be removed.

The result is still a complete and self-supporting filter element of thesize and shape of the four remaining sections. This permits themanufacture of a single size filter element which may be easily adaptedto apparatus of different sizes as desired.

Referring now to FIGURE 5, the method by which the filter element is`manufactured will now be described. FIGURE 5 illustratesdiagrammatically a mold or die assembly, including a lower plate 18 andan upper plate 20. Lower plate 18 is provided with a continuous seriesof cavities 22 which form the supporting frame pattern and which may beof any desired, but predetermined, configuration. Adjacent thecontinuous cavities 22 are raised portions 24, and within the raisedportions 24 are enlarged cavities 26. The upper plate 20 may besimilarly formed, or may be fiat as illustrated in FIGURE 5, dependingupon the type of frame structure desired in the filter element.

When it is desired to form a filter element, the batt of filter materialis placed between the die plates 18 and 20 and overlying the cavities22. When the filter batt 10 is properly positioned between the plates 18and 20, the plates are pressed together under pressure so that theraised portions 24 of the lower plate 18 compress the filter material 10against the upper plate, or against similar projections if such areprovided in the upper plate to seal the cavities 22 and prevent flow ofmaterial past the projections 24. The enlarged cavities 26 prevent themold or die plates 18 and 20 from compressing the main body of thefilter material 10. When the two plates 18 and 20 are properly placedtogether and under the required pressure, the material forming the framestructure is injected into the cavities 22 in any well known manner, thematerial being heated and in a liquid form to flow evenly through thecontinuous cavities 22. The liquid plastic envelopes the portions of thefoam material overlying the cavities 22, diffusing into and filling theinterstices therein, as shown in FIGURES 2 and 4 of the drawing. Afterthe material is injected into the cavities, it is allowed to cure, atwhich point it will harden and have incorporated in it the portions ofthe filter batt 10 overlying the cavities 22. After the material iscured, it is removed from the mold or die and the resultant structure issufficiently self-supporting to be used in the desired apparatus.

Referring now to FIGURES 3 and 4, another type of filter element isillustrated in which a filter batt 30 is surrounded by a suitable framestructure 32 and which has been formed in the manner above described.Additionally, in the element shown in FIGURES 3 and 4, projections 34are provided at spaced points along the periphery of the supportingframe 32 to form suitable fastening devices for the apparatus into whichthe filter element is placed. Such apparatus may be an air conditioneror the like, and suitable spring clips or other cooperating fasteningmeans engage the projections 34 in any well known manner to secure thefilter element in place. It is apparent that any type of fastening meansmay be integrally formed with the supporting frame 32 in the mold or diein which it is manufactured. Similarly, the fastening devices orfastening means may be located anywhere on the supporting frame, itbeing only necessary that they correspond with the location of thecooperating fastening means on the apparatus.

Referring now to FIGURES 2 and 4, a difference in the structure of theframe is apparent. The filter element illustrated in FIGURE 2 isprovided with a supporting frame 12 which extends outwardly from eithersurface of the filter batt 10. On the other hand, the filter elementillustrated in FIGURE 4 has the supporting frame 32 extending from onlyone surface of the filter batt 30. The diagrammatic illustration ofFIGURE 5, wherein the continuous cavity 22 is formed only in the lowerplate 18, illustrates how the support structure 32 of the filter elementof FIGURE 4 may be formed. If additional continuous cavities are placedin the upper plate 20, similar to those of the lower plate 18, asupporting frame structure such as found in FIGURE 2 would be formed. Ineither instance, the material of the filter batt is compressed adjacentthe continuous cavities to prevent the flow of liquid plastic materialfrom the cavities to the enlarged central cavities 26 and thus into thebody of the filter batt. As the liquid plastic material hardens orcures, the foam filter material is incorporated therein and be- 4 comesan integral part therewith to form the self-supporting lter elementstructure.

In the foregoing, filter elements have been described which havesufiicient strength to support themselves in a planar position. However,by'proper selection of materials and by properly dimensioning thevarious parts, it is possible to have a self-supporting filterelement'which is also of sufficient fiexibility to provide a belt ofvfilter material for use in other types of apparatus.

Reference is now made to FIGURE 6 wherein an elongated batt of filtermaterial 40 is provided with a supporting frame 42 in the mannerpreviously described. The supporting frame 42 extends at least aroundthe peripheral edges of the elongated filter batt 40 and is ofsufiicient flexibility to be formed into the belt shape and to berotated within the apparatus in which it is used. Suitable cross framemembers 46 between the peripheral sections 44, and properly spacedtherealong, may be provided, if necessary and desirable, to support thefilter batt 40.

In actual practice, it has been found that a filter element as abovedescribed may be constructed using a filter material of polyurethanediisocyanate ester, expanded to the desired density and properlydimensioned to provide the desired filtration characteristics. Asupporting frame material of polypropylene has been effectively injectedinto a suitably shaped die to incorporate the overlying portions of thefoam filter material and when cured has been of sufficient strength andrigidity to support the filter element. In the actual manufacture, ithas been found that with the die plates held together under a pressureof approximately 11,000 pounds per square inch and with thepolypropylene supporting frame material being injected into the moldparts at a temperature of from 200 to 300 Fahrenheit have beensatisfactory to form the filter element above described. It is evidentthat other materials are equally suited to the manufacture of the filterelements as are other temperature ranges and other pressure ranges inthe materials used.

Thus, a self-supporting filter element is provided which is extremelyeconomical to manufacture and extremely efficient in its operation. Thefilter material may be of a flexible and nonself-supporting type, and bythe method above described is easily and efficiently provided with asupporting frame structure which does not adversely affect the filteringcharacteristics and yet provides the necessary support. The methodpermits numerous possibilities in size, shape and ancillary parts of thefilter element, making it possible to utilize the method forsubstantially any filter element construction that is desired.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A self-supporting filter element comprising:

a batt of fiexible and nonself-supporting filter material;

a supporting border frame extending around the peripheral edge of thesurface of said batt and formed of a thermoplastic material diffusedinto and filling the interstices in the peripheral portion of said battin contact therewith, said portions of said batt extending substantiallyto the outer edges of said border frame and being compressed to preventflow therethrough; and

an intermediate frame formed integrally with and extending betweenelements of said border frame and formed of the same material as saidborder frame, said intermediate frame diffusing into and filling theinterstices in the portions of said batt in contact therewith, said lastnamed portions of said batt being compressed to prevent fiowtherethrough;

the parts of said filter element defined by adjacent elements of saidborder frame and said intermediate frame and between adjacent elementsof said intermediate frame and other elements of said intermediate framebeing complete self-supporting filter elements such that parts of saidself-supporting filter element outwardly of said adjacent elements ofsaid border frame and said intermediate frame are removable to changethe dimensions thereof. 2. The self-supporting filter element set forthin claim 1 wherein said border frame and said intermediate frame areformed only on one surface of said batt of lter material.

3. The self-supporting iilter element set forth in claim 1 wherein saidborder frame and said intermediate frame are formed on both surfaces ofsaid batt of filter material. 4. The self-supporting filter element setforth in claim 1 wherein said border frame and said batt of iiltermaterial are rectangular in shape, and said intermediate frame includesan element extending between opposite elements of said border frame.

S. The self-supporting filter element set forth in claim 4 wherein saidborder frame and said intermediate frame are formed on only one surfaceof said batt of filter material.

6. The self-supporting filter element set forth in claim 4 wherein saidborder frame and said intermediate frame are formed on both surfaces ofsaid batt of filter material. 7. The self-supporting filter element setforth in claim 1 wherein said border frame and said batt of ltermaterial are rectangular in shape, and said intermediate frame includeselements extending between opposite elements of said border frame toform a grid-like pattern over said lilter batt.

`8. The self-supporting lter element set forth in claim 1 and furtherincluding fastening means formed integrally with said border frame topermit mounting said filter element in a receptacle.

9. The self-supporting filter element set forth in claim 1 wherein saidbatt of lter material and said border frame are formed in an endlessloop.

References Cited UNITED STATES PATENTS 2,019,213 10/1935 Dahlman 55--514X 2,521,984 9/1950 Lang 55-486 2,852,094 9/1958 SaWle.

2,881,859 4/1959 Nutting 55-354 X 2,886,481 5/1959 Swan.

3,017,698 1/ 1962 Hambrecht et al.

3,082,587 3/1963 Brimberg 55-495 3,142,550 7/1964 Kuehne 55-4953,183,285 5/1965 Boylan 55--490 X 3,183,286 5/1965 Harms 264-271 X3,235,633 2/1966 Holloway et al. 55-502 X HARRY B. THORNTON, PrimaryExaminer.

B. NOZICK, Assistant Examiner.

Notice of Adverse Decision In Interference In Interference No. 97 ,337involving Patent No. 3,407,576, R. T. Staunton, SELF-SUPPORTING FILTERELEMENT, nal judgment adverse to the patentee was rendered Oct. 31,1972, as to claims l, 2, 4, 5, 7 and 8.

[Oficial Gazette December 12, 1972.]

1. A SELF-SUPPORTING FILTER ELEMENT COMPRISING: A BATT OF FLEXIBLE ANDNONSELF-SUPPORTING FILTER MATERIAL; A SUPPORTING BORDER FRAME EXTENDINGAROUND THE PERIPHERAL EDGE OF THE SURFACE OF SAID BATT AND FORMED OF ATHERMOPLASTIC MATERIAL DIFFUSED INTO AND FILLING THE INTERSTICES IN THEPERIPHERAL PORTION OF SAID BATT IN CONTACT THEREWITH, SAID PORTIONS OFSAID BATT EXTENDING SUBSTANTIALLY TO THE OUTER EDGES OF SAID BORDERFRAME AND BEING COMPRESSED TO PREVENT FLOW THERETHROUGH; AND ANINTERMEDIATE FRAME FORMED INTEGRALLY WITH AND EXTENDING BETWEEN ELEMENTSOF SAID BORDER FRAME AND FORMED OF THE SAME MATERIAL AS SAID BORDERFRAME, SAID INTERMEDIATE FRAME DIFFUSING INTO AND FILLING THEINTERSTICES IN THE PORTION OF SAID BATT IN CONTACT THEREWITH, SAID LASTNAMED PORTIONS OF SAID BATT BEING COMPRESSED TO PREVENT FLOWTHERETHROUGH; THE PARTS OF SAID FILTER ELEMENT DEFINED BY ADJACENTELEMENTS OF SAID BORDER FRAME AND SAID INTERMEDIATE FRAME AND BETWEENADJACENT ELEMENTS OF SAID INTERMEDIATE FRAME AND OTHER ELEMENTS OF SAIDINTERMEDIATE FRAME BEING COMPLETE SELF-SUPPORTING FILTER ELEMENTS SUCHTHAT PARTS OF SAID SELF-SUPPORTING FILTER ELEMENT OUTWARDLY OF SAIDADJACENT ELEMENTS OF SAID BORDER FRAME AND SAID INTERMEDIATE FRAME AREREMOVABLE TO CHANGE THE DIMENSIONS THEREOF.